The normal right ventricle (RV) has three components: the inlet (including tricuspid valve, chordae tendineae, and papillary muscles), the trabeculated apical portion, and the infundibulum or outflow tract. Under typical conditions, the right heart receives the systemic venous return and pumps to the low-impedance pulmonary vascular bed.¹ In the absence of a shunt lesion, the RV has identical output to the left ventricle but pumps at one-sixth of the left ventricular pressure. Right-sided congenital heart disease involving the tricuspid valve, RV outflow tract, or RV chamber itself can disrupt the normal hemodynamics. Valve regurgitation leads to volume overload and compensatory right heart chamber dilation. Obstruction of flow through the outflow tract results in high RV pressure and compensatory hypertrophy of the myocardium. Because of ventricular interdependence (related to the shared interventricular septum and constraining pericardium, among other factors), pressure or volume overload of the RV can impact the function and morphology of the left ventricle.¹

Obstruction of blood flow out of the RV can occur proximal to the pulmonic valve, at the pulmonic valve, or distal to the pulmonic valve. These lesions may occur in isolation or in combination. It is important to identify the location and nature of the obstruction, which in some cases may require multiple imaging modalities.² After percutaneous or surgical relief of pulmonary valve obstruction, pulmonary regurgitation (PR) is the most common complication and requires close surveillance for adverse impact on the RV.

A double-chambered right ventricle (DCRV) is defined as obstruction of blood flow at or within the sub-infundibular ventricle. It consists of a high-pressure proximal chamber and a low-pressure distal chamber.

DCRV is a rare congenital anomaly seen in approximately 0.5% to 2.0% of all congenital heart disease cases.³ Some cases of DCRV may be secondary, related to compensatory muscular hypertrophy from a pressure-loading lesion, and therefore the true incidence of primary DCRV (muscular hypertrophy with no clear other cause) may be lower.⁴ To date, there is no genetic mutation that has been associated with DCRV.

The obstruction in DCRV can be due to thickened trabeculations, anomalous muscle tissue, or an aberrant and hypertrophied moderator band (ie, septomarginal trabeculation).³ Fibromuscular thickening of the infundibulum alone is often referred to as subvalvular pulmonic stenosis (PS). This may be a form of DCRV or secondary to pressure overload of the RV, as described earlier. DCRV is commonly associated with other congenital heart defects. Isolated DCRV is almost always associated with a membranous ventricular septal defect, often small. In addition, DCRV is associated with tetralogy of Fallot, Ebstein anomaly, and double outlet RV.⁵

Adults with DCRV can present with dyspnea, syncope, angina, and exertional intolerance. On examination, a holosystolic murmur is present along the lower left sternal border. Given the RV hypertrophy, an RV heave may be appreciable as well as a thrill.

Differential Diagnosis: Other causes of intraventricular obstruction to blood flow include muscle hypertrophy at the infundibulum, which can occur in PS as well as hypertrophic cardiomyopathy.

Indications for intervention on DCRV include (a) moderate or greater obstruction (defined as peak velocity >3 m/s by Doppler echocardiography) with symptoms of heart failure, (b) exercise intolerance, or (c) severe asymptomatic obstruction (peak velocity >4 m/s by Doppler echocardiography).⁸ Medical therapy has not been demonstrated to be beneficial. Although balloon valvotomy has been reported, its efficacy in most patients is yet to be established.⁹ Surgical repair typically involves a transatrial or transventricular approach. Postoperatively, clinicians must be wary of conduction system disease, particularly right bundle branch block as the right bundle branch runs in the septomarginal trabecula and moderator band. Surgical resection by an experienced congenital surgeon tends to be definitive with excellent long-term results.¹⁰,¹¹

Valvular PS is a common congenital anomaly. Mild-to-moderate cases may be diagnosed for the first time in adulthood when a murmur is auscultated. Additionally, severe PS treated during childhood has excellent long-term survival, and therefore many adult patients born with PS now require long-term follow-up.¹²,¹³ Three types of valvular PS occur: dome-type, dysplastic, and unicuspid/bicuspid pulmonic valves (Table 108.1).

Valvular PS makes up almost 90% of congenital RV outflow tract abnormalities.¹⁴ The dome-type valve is the most common type of congenital pulmonic valve abnormality. Although there is no identified genetic abnormality, there does appear to be a chance of inheritance (<5%). Pulmonary valve dysplasia is commonly associated with Noonan syndrome and chromosome 12 mutation, with an autosomal dominant inheritance with variable penetrance.¹⁵ Unicuspid, bicuspid, or quadricuspid pulmonic valves are rare, and bicuspid valves may be associated with tetralogy of Fallot. Any of the valve morphologies may also have associated pulmonic regurgitation, though stenosis is more typical.

Ongoing pressure overload to the RV can cause hypertrophy and fibrosis, which may cause right-sided diastolic and
eventually systolic dysfunction. Thus, patients with PS can present with right-sided heart failure or exertional symptoms (eg, dyspnea, syncope, chest pain) related to inadequate pulmonary blood flow with exertion and possibly RV ischemia. Examination findings depend on the severity of the stenosis. In severe disease, a prominent “A” wave in the jugular venous pulse is common. An RV heave is commonly present on cardiac palpation. Heart sounds are notable for an ejection click that decreases in intensity with inspiration and as PS progresses, and may no longer be audible as it moves closer to S1. Wide splitting of S2 will reflect the prolonged pulmonic ejection time. A right-sided S4 is expected in those with a prominent “A” wave in the jugular venous pressure. The systolic ejection murmur peak moves later in systole as severity progresses. Cyanosis can be observed when significant PS occurs in the setting of atrial septal defect or patent foramen ovale, related to high right atrial pressure and right-to-left atrial shunting.

Differential Diagnosis: Other causes of RV outflow tract obstruction should be considered.

ECG in advanced disease (RV systolic pressure >60 mm Hg) will demonstrate RV hypertrophy, right atrial enlargement, and right axis deviation. Chest x-ray often reveals findings of preferential flow into the left pulmonary artery (PA) including increased vascular fullness in the left lung and dilation of main and left PAs (often referred to as “witch’s nose,” Figure 108.2). These findings are more common in dome-type valvular PS compared to valve dysplasia.

When PS is identified, it is critical to assess the severity of obstruction; this is typically done by Doppler echocardiography. PS is considered mild when the peak gradient is <36 mm Hg, moderate with peak gradient 36 to 64 mm Hg, and severe with peak gradient >64 mm Hg or mean gradient >35 mm Hg in the setting of normal RV function. In addition to quantifying the degree of stenosis, assessment of the degree of regurgitation (if present) is necessary, as this has therapeutic implications (see below).

In patients who are pregnant, isolated PS tends to be well tolerated, even if severe. The mother tends to do very well, though the neonates tend to have higher rates of premature delivery and perinatal mortality (4.1%).¹⁸ Percutaneous balloon valvuloplasty during pregnancy can reduce neonatal risk.

Supravalvular PS involves narrowing of the main or branch PA. It can occur in isolation, in association with RV outflow tract stenosis, or in the setting of a genetic abnormality associated with multiple other cardiac defects. In those with prior surgery, it can also occur at sites of prior interventions (eg, PA banding; Blalock-Thomas-Taussig, Potts, or Waterston shunts; or Jatene arterial switch/post-Lecompte maneuver).¹⁹ Native peripheral PA stenosis occurs infrequently in congenital heart disease, and the incidence of postsurgical peripheral PA stenosis is not well defined.²⁰

Native isolated peripheral PA stenosis is commonly seen either at the main PA bifurcation or in the left PA at the site of the closed ductus arteriosus. Postsurgical peripheral PA stenosis occurs as a complication of scarring at takedown sites of prior palliative shunts or surgical corrective procedures.

Isolated peripheral PA stenosis is frequently associated with ventricular septal defect. There are multiple genetic syndromes associated with peripheral PA stenosis including Alagille syndrome, Keutel syndrome, Williams syndrome, LEOPARD syndrome, Noonan syndrome, and congenital rubella. Peripheral PA stenosis can also occur in the setting of tetralogy of Fallot.

Patients with peripheral PA stenosis present similarly to valvular PS with dyspnea on exertion, right-sided heart failure, and exertional light-headedness. Examination may demonstrate a systolic or even continuous murmur. There will also be evidence of RV hypertension on examination, similar to findings in valvular PS.

ECG has no specific findings other than RV hypertrophy. Chest x-ray may show a relatively small vascular pedicle as well as increased lucency in the lung fields if the stenosis is unilateral. Transthoracic echocardiography may raise suspicion for increased pressures in the main PA, though two-dimensional (2D) visualization of the PAs can be challenging, especially in adult patients. Parasternal imaging with color flow and continuous-wave Doppler is the most helpful for identifying peripheral PA stenosis on echocardiography. Cross-sectional imaging with CT or MRI is generally required in the evaluation of peripheral PA stenosis.²¹ In addition, direct measurement of pressure gradients in the catheterization lab can be very helpful to simultaneously assess the severity of stenosis and identify its precise location with pulmonary angiography (Figure 108.4).

Intervention of peripheral PA stenosis is warranted for any symptomatic patient, those with decreased pulmonary blood flow, or those with significantly elevated RV pressures on echocardiography or catheterization. Those patients with PA stenoses that are not significant should continue to be monitored every 3 to 5 years with interval cross-sectional imaging in addition to ECG, chest x-ray, transthoracic echocardiography, and exercise testing. In a patient with severe obstruction, percutaneous peripheral intervention is the first step. Percutaneous balloon angioplasty, sometimes with stent placement, is commonly performed for branch PA stenosis. After percutaneous intervention, patients require close follow-up; up to a quarter will require repeat intervention for recurrent stenosis.⁸

Pulmonary atresia with intact ventricular septum is characterized by complete obstruction of flow through the RV outflow tract, often with RV and tricuspid valve hypoplasia. Pulmonary atresia with intact ventricular septum is rare, estimated to occur in 4 to 5 per 100,000 live births,²² and has no known genetic or gender association.²³

Pulmonary atresia with intact ventricular septum is primarily defined by complete obstruction of flow through the RV outflow tract. Membranous atresia, related to atretic pulmonary valve and small annulus, occurs in 75% of cases, whereas the remaining 25% have muscular atresia, or obliteration of the muscular infundibulum.²²